A low level of physical activity has been associated with depression, and increased physical activity has been found to have a positive effect on mood. However, the association between maximal oxygen uptake (VO2max) and mood has been poorly studied. In this study VO2max (ml/kg per min) was measured in a sample of 1,519 men aged 46-61 years during a cycle ergometer test by using respiratory gas exchange. Men with a history of psychiatric disorder or serious physical illness were excluded. Depressive symptoms were assessed using the 18-item Human Population Laboratory Depression Scale (HPL). Those who scored 5 or more in the HPL were considered to have elevated depressive symptoms.

The participants were classified into quartiles according to the VO2max. Those in the lowest quartile had a more than 3-fold (OR: 3.42; 95% CI: 1.65-7.09; p < 0.001) higher risk of having elevated depressive symptoms compared with those in the highest quartile, even after adjusting for several confounders (OR: 3.38; 95% CI: 1.60-7.14; p < 0.001).

In conclusion, low VO2max is associated with having elevated depressive symptoms in middle-aged men.